This is a continuation in part of my application Ser. No. 234,312, filed Mar. 13, 1972, now abandoned. Governmental requirements for automobile passenger restraint systems include an inflatable bag that momentarily and temporarily restrains a passenger during the critical instant of a collision impact. For safe and successful use, the bag must be inflated in a very short time and thereafter deflated to release the passenger. The gas used to inflate the bag must be cool enough to avoid damage to the bag and injury to the passenger. For similar reasons, it is important that hot particles do not reach the interior of the bag. The gasses used must have a low toxicity and for this reason carbon monoxide, nitrogen oxides, sulphur compounds and the like are undesirable.
In some embodiments, deflation of the bag is obtained by using a fabric of controlled porosity since the entire phenomenon of passenger restraint is kinetic. Thus, the bag rapidly inflates without a substantial pressure gradient across the fabric and little gas flows therethrough during the short time interval of inflation. Substantial pressures may be created in the bag as it restrains a passenger during impact and the energy of the passenger is dissipated over a period of time which is controlled by the porosity of the fabric. Quite a bit of gas is pushed out of the bag during this time. Subsequently the bag deflates as gas flows through the fabric over a somewhat longer period of time. Since the gas in such an embodiment is dissipated in the passenger compartment of the automobile in close proximity to the passenger being restrained, low temperature and low toxicity are of appreciable importance. In addition, it is important that the gas be relatively free from smoke so as not to inhibit visibility by the driver or passengers and avoid any skin, eye or respiratory irritations that might arise from smoke particles. It is, therefore, desirable to provide pyrotechnic compositions that burn to produce a large volume of relatively cool, non-toxic, smoke-free gas in a very short time interval for inflating a passenger restraint bag.
The pyrotechnic composition must be sufficiently stable to sustain the temperature, vibration and other environmental characteristics of an automobile for a prolonged period without degradation of performance. In a typical embodiment, about 265 grams of pyrotechnic composition may be employed for inflating a five cubic foot bag. For this reason it is desirable that the composition be relatively inexpensive.